The use of various compositions employing blends of ethylene polymers and copolymers in admixture with various other modifying ingredients as insulating materials and/or coverings in electrical wire applications is well known in the art.
Typically, a suitable polymeric resin material may be modified via the addition of a variety of specific additives in order to enhance various characteristics of the basic polymeric material in such a way as to obtain a composition which exhibits such enhanced physical characteristics as may be thought to be important in a particular application in which the resultant material is to be utilized.
Cross-linked ethylene-containing polymeric compositions are generally known to exhibit good physical properties such as tensile strength and low dielectric losses. However, recent demands for superior jacketing and/or insulating compositions for use on wire and cable which may require a combination of superior resistance to the propagation of flame together with low levels of smoke and toxic byproduct emission when subjected to heat and flame while, at the same time, high tensile strengths and resistance to moisture, abrasion and weathering, as well as resistance to various chemicals and oils, have rendered the materials heretofore available in the art inadequate.
Representative of the state of the art's knowledge vis-a-vis various compositions which have been heretofore taught to be useful combinations as covering materials in various electrical applications are the following:
U.S. Pat. No. 4,001,128 to Penneck, which issued on Jan. 4, 1977, relates to a filler system for polymers which provides a high voltage insulation material which is resistant to tracking. Penneck discloses a combination of alumina trihydrate together with a chemically treated silica filler in combination with various polymeric materials as having improved tracking resistance in high voltage insulating applications. Ethylene-vinyl acetate copolymers are disclosed amongst those which may be modified utilizing the disclosed fillers. Such insulating materials may also be cross-linked.
U.S. Pat. No. 3,936,572 to MacKenzie, Jr. et al., which issued on Feb. 3, 1976, describes a curable composition which is especially adaptable for use as insulation for wire and cable, comprising an ethylene-containing polymeric member, a curing agent and a silicone fluid having a specific viscosity. Such materials may also include carbon black and a mineral filler.
U.S. Pat. No. 4,022,945 to MacKenzie, Jr. et al., which issued on May 10, 1977, discloses a fire retardant system for polymeric compositions comprising a combination of a halogen-containing hydrocarbon and an oxide of iron. The disclosed compositions may include ethylene-vinyl acetate copolymers in admixture with various modifiers in addition to the specific flame retardant agents disclosed as components of the insulation material.
U.S. Pat. No. 4,085,249 to Taniguchi et al., which issued on Apr. 18, 1978, teaches a semi-conductive composition having controlled strippability made from cross-linked ethylene polymer based insulation compositions, comprising chlorinated ethylene-vinyl acetate copolymer containing about 3 to 40 percent by weight of chlorine and conductive carbon black.
U.S. Pat. No. 4,140,818 to Dave, which issued on Feb. 20, 1979, relates to cured insulation compositions which are freely strippable from the encased conductors and incorporate the use of small amounts of (a) a dialkyl tin diester, (b) N,N'-ethylene bis-stearamide or similar waxy compositions, and (c) certain 3-amido-1,2,4-triazoles. The use of the combination of the foregoing materials in known insulation formulations is taught to render the resultant insulation freely strippable.
U.S. Pat. No. 2,888,424 to Precopio et al., which issued on May 26, 1959, discloses compositions comprising polyethylene and polyethylene blends, dicumyl peroxide and fillers selected from the group consisting of silica, carbon black, alumina and calcium silicate as well as the cured products thereof, to yield products having improved physical properties.
U.S. Pat. No. 4,134,812 to Sasaki et al., which issued on Jan. 16, 1979, relates to a method of manufacturing shaped articles of a cross-linked poly-.alpha.-olefin composition via irradiation with an electron beam which includes the step of blending the poly-.alpha.-olefin with a composition miscible therewith which composition may contain an acetylenic linkage.
U.S. Pat. No. 2,057,690 to Moss, which issued on Oct. 20, 1936, relates to the production of electrical devices utilizing plasticized polymerized vinyl acetate and other polymerized vinyl compounds to produce compositions having high electrical resistance suitable for insulating electrical conductors.
None of the foregoing prior art teachings suggest the particular compositions which are the subject of the present application which exhibit a unique combination of superior resistance to the propagation of flame along, with an extremely low level of smoke emission and a relatively low level of toxic byproduct emission when such compositions are subjected to heat or flame while, at the same time, exhibiting superior tensile strength and resistance to weathering, moisture and too many chemicals and oils.
It is, therefore, an object of the present invention to provide a cross-linked polyolefin composition for use as a jacketing material in high voltage wire and cable applications which jacketing composition possesses a superior resistance to the propagation of flame, a low smoke emission level and low emission of toxic byproduct when subjected to heat or flame as well as lower water absorption characteristics and high resistance to weathering, oils and chemicals.
It is a further object of the present invention to provide a cross-linked polyolefin insulating composition for use in low voltage wire and cable applications which insulating material possesses superior resistance to the propagation of flame, a low smoke emission level and low emission of toxic byproducts when subjected to heat or flame as well as low moisture, absorption characteristics and high resistance to weathering, oils and chemicals.
It is a further object of the present invention to provide for a novel jacketed wire or cable for high voltage applications wherein the jacketing is comprised of a polyethylenevinyl acetate copolymer, magnesium silicate and alumina hydrate in major proportions and, in minor proportions, carbon black, polymerized 1,2-dihydro 2,2,4 trimethyl quinoline, stearic acid, vinyl-tris (.beta.-methoxethoxy)silane, triallyl cyanurate, and dicumyl peroxide in anhydrous aluminum silicate.
It is yet a further object of the present invention to provide for a novel insulated wire or cable for low voltage applications wherein the insulation is comprised of a polyethylenevinyl acetate copolymer, magnesium silicate and alumina hydrate in major proportions, and, in minor proportions, carbon black, polymerized 1,2-dihydro 2,2,4 trimethyl quinoline, stearic acid, vinyl tris (.beta.-methoxethoxy)silane, triallyl cyanurate, and dicumyl peroxide in anhydrous aluminum silicate.
These and other objects of the present invention will become apparent from the following description of the invention.